Health Disparities

The health status of racial and ethnic minority groups in the U.S. has improved steadily over the last century. Despite such progress, disturbing disparities in health persist between majority and minority populations. Demographic projections predict a substantial change in the racial and ethnic makeup of the older population, heightening the need to examine and reduce differences in health and life expectancy. Research to date has shown that health disparities are associated with a broad, complex, and interrelated array of factors: Disease risk, diagnosis, progression, response to treatment, caregiving, access to care, and overall quality of life each may be affected by variables such as race, ethnicity, gender, socioeconomic status, age, education, occupation, country of origin, and possibly other lifetime and lifestyle differences. In one recent study, investigators found that adjusting for reading recognition scores on an achievement test known as the WRAT-3 attenuated racial group differences on most cognitive tests between older white and African Americans matched on years of education. The WRAT-3 scores served as an estimate of quality of education, and this finding suggests that it is quality and not necessarily years of education that may affect cognition in later years.

The NIA is committed to addressing health disparities through its research programs. For example, Satellite Diagnostic and Treatment Centers, part of the national Alzheimer’s Disease Centers (ADC) Program, have successfully recruited African Americans, Hispanics, Native Americans, and American Indian/Alaska Natives to AD prevention and treatment studies. Researchers on the NIA’s Religious Orders Study have made a major effort to enroll African American members of the Catholic clergy; the nature of the study population enables the etiology and pathology of AD to be established among individuals with similar educations, occupations, socioeconomic status, and lifestyles.

The NIA is also participating with the National Institute of Environmental Health Sciences, the National Cancer Institute, and the NIH Office of Behavioral and Social Sciences Research on new Centers for Population Health and Health Disparities, which are designed to support interdisciplinary research to examine how the social and physical environment, behavioral factors, and biologic pathways interact to determine health and disease in populations. To date, NIH has awarded eight grants in total from this initiative. NIA is supporting two: A series of inter-related studies involving a cohort of older adults of Puerto Rican origin in the Boston area, with particular attention to specific stressors affecting that community, determining the effect of these stressors on allostatic load (“wear and tear” on body systems resulting from stress) and, in turn, on disease-specific outcomes, and an analysis of data from the Health and Retirement Study and the Panel Study of Income Dynamics to determine neighborhood factors that impact the functional and cognitive aspects of the disabling process in the elderly. The latter project is coordinated with an NIEHS-awarded Center grant.

Where a patient lives determines likelihood of knee surgery. Researchers used Medicare fee-for-service claims data for 1998-2000 to determine the incidence of knee arthroplasty between Hospital Referral Regions by sex and race or ethnic group. They found that in some regions, the rate of knee arthroplasty for black women was significantly lower than that for white women (e.g., Washington DC; Atlanta; Chicago), whereas in other regions (e.g., Los Angeles; Manhattan; Birmingham), the rates were roughly equal. Around 35 percent of the national differences in arthroplasty rates for black women and 95 percent of the national differences for Hispanic women are explained by the fact that black and Hispanic women are more likely to live in regions with lower rates for all races and ethnic groups. In the study, residential segregation by race (among black women) and low income (among Hispanic women and black men) were associated with larger differences in arthroplasty rates. Furthermore, arthroplasty rates were consistently lower among black men than among white men in nearly every region, and in some areas the rates for black men were less than one third those for white men. These persistent differences cannot be explained on the basis of financial or geographic barriers alone, since the pattern was not apparent for black women living in the same neighborhoods. These variations underscore the importance of examining geography and sex in determining racial or ethnic barriers to health care.

Contributions of major diseases to disparities in mortality. Researchers in a recent study found that although many conditions contribute to socioeconomic and racial disparities in potential life-years lost, a few conditions account for most of these disparities – smoking-related diseases in the case of mortality among persons with fewer years of education, and hypertension, HIV, diabetes mellitus, and trauma in the case of mortality among black persons. These findings have important implications for targeting efforts to reduce existing disparities in mortality rates.

Selected Future Research Directions in Health Disparities

The NIA has implemented Healthy Aging in Neighborhoods of Diversity Across the Lifespan (HANDLS), a community-based study of health disparities among different racial, ethnic, and socioeconomic groups in Baltimore. The purpose of HANDLS is to disentangle the effects of race and SES on risk factors for morbidity and mortality, incidence and progression of pre-clinical disease, development and persistence of health disparities, and longitudinal health status and health risks. Unique to the HANDLS study is the use of two fully-equipped mobile research laboratories (MRVs) that enable investigators to collect data directly in the neighborhoods under study, establishing links with the community and increasing both the interest of potential participants and the retention rate. The pilot phase of the study was completed in December 2001, and the full-scope study is now being planned for implementation in 2004-2005.